In studies of the conversion of methylcyclopentane (MCP), n-hexane ( nC 6), 2-methylpentane (2MP), and 3-methylpentane (3MP) over a Pt/SiO 2 catalyst with an average Pt particle size less than 20 Å, it is found that MCP formation from acyclic hexanes is independent of residence time. Since a cyclic mechanism via a five-membered ring intermediate is the predominant hexane isomerization route, this observation suggests that isomerization is best approximated by a sequential reaction, ( nC 6, 2MP, or 3MP) → k 1 MCP → k 2 ( nC 6, 2MP, and 3MP), in which the quasi-steady-state approximation, d[ MCP] dt = 0 , is applicable. The quasi-steady-state approximation requires that k 2 ⪢ k 1 viz., the five-ring closure of hexane to MCP is rate-controlling. k 1 is established to be rate-controlling by experiments with mixed hexane and MCP feeds. Also, the formation of MCP from the acyclic hexanes is found to be independent of time on stream while the generation of isomerized products decreases by 30–40% with time. Based on a hydrodynamic analog of a sequential reaction, this observation indicates that k 1 and k 2 deactivate at the same rate thereby maintaining k 1 k 2 constant with time on stream. This argument implies that the ring closure of hexane to MCP and the ring opening of MCP occur on the same site and is consistent with microscopic reversibility which requires a common intermediate. Kinetic parameters calculated from the sequential reaction model using the quasi-steady-state approximation show that five-ring closure between two primary carbon atoms (2MP and 3MP) is about three times faster than that between a primary and a secondary carbon atom ( nC 6). For ring opening of five-ring intermediates, the reaction order in MCP concentration is higher with acyclic hexane feeds than with MCP feed due to a lower surface hydrocarbon coverage with the former feedstocks. During isomerization of the acyclic hexanes, hydrogenolysis to smaller molecules is a competing reaction pathway. For 2MP and 3MP, the rupture of the CC bond in β-position to the tertiary carbon atom is preferred and with the β bond in 3MP being more reactive than that in 2MP. In the case of nC 6, the center CC bond ruptures three times faster than the other CC bonds. These observations are in good agreement with literature data.